There are many known rotary spreaders. Examples on spreaders are described in EP1382236, U.S. Pat. Nos. 1,769,302, 5,123,598 and 5,203,510.
U.S. Pat. No. 4,580,730 describes a rotary spreader for particulate material having a hopper for the particulate material and an impeller adapted to broadcast the material as it is discharged from the hopper. Multiple fin lengths are provided on the impeller to throw the particulate material in different radial distances aiming at providing better particulate distribution. However, the practical use of such a rotary spreader has shown that skewing of the broadcast pattern still exists. Such skewing is a problem in many situations.
U.S. patent application 20030443702 published as U.S. 2003192968 is hereby incorporated by reference and describes a spreader with a movable deflector. The spreader provides a control of pattern of dispensing material from a yard spreader. A remaining problem with the spreader is that skewing of the broadcast pattern still exists. The skewing increases with the angle of spread. A distribution of spread material distributed by a spreader similar to the spreader according to U.S. 20030443702 is shown in FIG. 1. The distribution was measured by use of cylindrically shaped cans standing on a line in the direction of movement of the spreader. The number of pieces of granulated material was counted for each can.
Spreaders according to the art may have one feature to stop the flow of material to a rotatable plate in the case the spreader stops, and second feature to control the amount of material dispersed from the hopper to the rotatable plate.
The inventors have found that for many applications the existing art is not sufficient when it comes provide spreaders with a large spread area and that at the same time avoids skewing of the broadcast pattern.